Preliminary data-collections indicate there may be a specific type of opioid receptor related to opioid's ability to reinforce its own intake. The possibility of a specific receptor became apparent by studying diprenorphine, a mixed agonist-antagonist which antagonizes many events of morphine but which shows signs of having capability to elicit opioid-positive-affect. The research to be done will follow the preliminary findings and explore the dimensions of diprenorphine's effects as well as studying diprenorphine's site to action. Among people, TRC, the active ingredient of marijuana, clearly produces signs of positive affect. Yet, we have little or no capability of studying THC-elicited positive affect in laboratory subjects, such as rats. Consequently, we have little information concerning how THC may induce positive affect which is one the features by which THC sustains its own intake. Research will be done leading to the capability of measuring THC-elicited positive affect among rats and, thereby, begin the process of studying how THC achieves its positively reinforcing effects. It is clearly a possibility that opioids and THC's rewarding effects are mediated by way of similar processes. Research is proposed which will delineate which neurochemical systems are critical to both opioid and THC's rewarding features.